Joining cord ends



Nov. 3, 1964 H. WESTMIJZE ETAL JOINING CORD ENDS Filed Nov. 15, 19623,155,062 HWING QGRD ENDS Herman Westmijze, Velp, and Leendert Ploegen',arnhem, Netherlands, assigner-s to NN. nderzoekingsinstituut Research,Arnhem, Netheriands, a corporation of the Netherlands Filed Nov. l5,i952, Ser. No. 238,33@ Claims priority, application Netherlands Nov. 30,1961 3 Claims. (Cl. i12-412) The invention relates to the joining ofcord ends in such a manner that two cord ends are laid side by side inopposite directions and are joined together by means of a zig-zaggedseam. The invention also relates to cords comprising such joints, tocord fabrics comprising such cords, and to products consisting entirelyor partly of such cords or cord fabrics.

By cords are also to be understood hereinafter all those products whichare to be regarded as cords in the most extended sense of the word. Thisincludes in particular cords used to reinforce the canvas of drivingbelts, motor car tires, and like products, but it also comprisestrimming cords, tying cords, cables, etc. Moreover, the cords may varywidely as far as their chemical compositions are concerned, includingnatural animal and vegetable bers such as cotton, linen and the like, aswell as synthetic fibers of which the rayons, nylons and polyolenes maybe considered representative.

Particularly in cases Where the cords are used as reinforcement the cordjoints are to meet very 'exacting requirements. In this connection muchhas been done already for the improvement of joints.

Heretofore such edorts were largely directed to using different knotpatterns for tying the cord ends together. 'Ihe most widely varyingknots were used, but they all showed great drawbacks. The main drawbackis the high loss of strength of a knot relative to the cord. Generally,the strength of cord knots is not more than 60% of the cord strength.

It follows then, when the cords so joined are used in further processesthe knots may break or come undone and that in a product made of thiscord there may be latent weak spots. These weak spots are particularlyundesirable if the cords are incorporated in products subject toconsiderable stress such as motor car tires or driving belt canvas.

An additional disadvantage to joining cords by means of knots consistsin that at the knot there are practically always projecting loosefilaments or cord ends. These may give rise to entanglements between thevarious cords or to the cords getting caught on the after-processingmachines.

More recently it has been proposed to solve the problem by joining thetwo cord ends, which are laid side by side and in opposite directions,by means of a Zigzagged seam. This method has great advantages overknotting as the strength of the joint when loaded for a short time is90% of that of the cord. Moreover, this joint is initially free fromprojecting cord ends. An additional and also very important practicaladvantage is that this method can be carried out more rapidly than theknotting, it being possible for the joints to be made by means of anappropriate sewing machine, which is not nearly so monotonous or tiringas knotting.

In spite of these advantages, this method still has serious drawbacks inactual practice. Although a joint strength equal to 90% of the cordstrength represents a considerable improvement over the'strength of aknotted joint, it has been found in practice that the joints should bestill stronger.

For example, this 90% strength of the sewed joints cannot be maintainedif a cord joined in this way is kept States Patent O i 3,155,%Z PatentedNov. 3, 1964 ice under tension for a relatively long time in thesubsequent processing or use.

The after-process may, for instance, consist in additional stretching ofthe cord or in impregnating it while keeping it under tension, and thesubsequent drying of the cord thus treated.

The decrease in strength is due to the fact that the tension is largestat the extreme ends of the joints. The extreme or end stitches, whichare weak by nature, may then come loose or break, upon which the tensionat the next, adjoining stitches is highest. This process continues andthe length of the zig-zagged seam becomes smaller and smaller so thatthe strength of the joint gradually declines. After some time, thelength of the seam is reduced to a minimum and the seam will then ,breakspontaneously along its entire length. The fact that the seam graduallyloosens moreover causes the formation of loose projecting cord ends.This is attended with the above-described undesirable effects'.

We have found, however, that all the aforementioned drawbacks may beavoided if the cord ends are joined by our improved method ashereinafter described.

It is an object of the present invention to provide an improved methodfor joining two cords.

Another object is to provide a method whereby two cords may be joinedreadily by an improved seam using semiautomatic means such as a sewingmachine.

A further object of the invention is the provision of an improved jointseam of relatively simple construction having a strength at least equalto that of the cords themselves.

Still another object is the provision of a seam for joining two cords inwhich the stitches forming said seam are so arranged that tensionalforce applied to the joint is distributed substantially uniformly amongthe stitches forming the seam.

These and other objects will become readily apparent to those skilled inthe art from the accompanying drawings and the following description.

The present invention consists in that the joining is carried out withthe two cord ends laid side by side and in opposite directions and theends sewn together by means of a zig-zagged seam, said seam changes atits ends into a looped seam such that the stitches are wound around oneof the cords and pulled through the other cord.

lf the cords are joined in this way, they do not tend to come loose orto break at the ends. Moreover, the strength of the joint can inpractically all cases be maintaned at more than of the cord strength,even when the cord is loaded under tension for a relatively long time.

This result may be explained as follows:

If two pieces of cord, which are joined so that their free ends are laidside by side, are subjected to a tensional force, there will prevail notension at the extremities of the two free ends, and the pieces of cordagainst the free end will be subjected to the full tensional force.Consequently, in these places the states of elongation in the two piecesof cord will be extremely different. As a result, the tendency of thecord pieces to shift relative to each other is strongest at their ends,so that with the ordinary zig-zagged seam the tension is highest inthose places. This' results in the progressive failure of the stitchesdescribed above.

By drawing the stitches at the ends only through one of the pieces ofcord, according to the invention, there remains in principle somefreedom of movement between said cord ends. When the joint thus made issubjected to some force, the wrapped piece of cord is to some eX- tentfree to move through the wrapping. As a result of the friction betweenthe adjacent cord ends, the load on the one piece of cord will graduallydecrease toward its free end, and the load on the other piece of cordwill gradually increase from its free end, and the seam joining the twocord ends will be loaded substantially uniformly along its entirelength.

The looped seams may be made in two Ways, namely such that the free endsof the cord sections are encircled or such that the stitches are pulledthrough the free ends.

It has been found that the joint can be made strongest according to theinvention if the stitches `are pulled through the free ends of the cordsections. When the joint is subjected to tensional force, the mechanicalload to which thesey free ends are subject is smallest at the loopedseam, Vso that these free ends are apparently the most capable ofstanding up to any weakening as a result of stitching.

A joint thus made is capable of withstanding a tensile load which is atleast as high as that of the cord. 'I he strength does not decline whenthe joint is loaded for a long time.

It is preferred that the stitches of the looped seam are spaced atcloser intervals than the stitches of the zigzagged seam.

This makes it possible for the overall length of the searn to be smallerwithout the looped seams being additionally weakened by the stitchpunctures. For these stitch punctures are in the cord ends which aresubject to little or no tension, whereas the actual Zig-zagged seam mustalong its entire length transfer the entire tensional force' to cordsections which are weakened little as possible by stitch punctures.

lt has been found that a satisfactory joint of minimum length can beobtained if the zig-zagged searn comprises at least zig-zag stitches andthe looped seam at least zig-zag stitches, and if the length of thezig-zagged seam is at least times the thickness of the cord, and thelength of the looped seams is at least 12 times the thickness of thecord.

In addition to its application to a method of joining the cord ends, theinvention also relates to the cords which are joined in this manner, andto cord fabrics comprising such cords, and to products consistingentirely or partly of these cords or cord fabrics. The cords and cordfabrics made according to the invention have been found of particularvalue if the cords are used for the purpose of reinforcing motor cartires or driving belts, the cord fabric forming the canvas of thesetires or belts. The motor car tires and the belts thus man factured areless likely to be subject to canvas ruptures.

For the purpose of explaining the invention there now follows adescription, with reference to a drawing, of a representative cordjoint, the invention, of course, not being limited to this singleexample. Many other specic cord joints, and other types of cord arewithin the purview of this invention` Referring now to the drawings, inFIGURE 1 there are shown two cords, l and 2. ln this example, the cordshave a thickness of 0.85 mm. each and are each made up of two strands ofmultilament rayon yarn. Each of these strands has a thickness of 1650denier. They are obtained by wet-spinning viscose into an acid spinningbath.

The cords 1 and 2 are laid side by side with their ends, along adistance of 7 cm., along which distance the ends are sewn together' bymeans of threads 3, use being made of a suitable sewing machine.

The seam is divided into two looped seam sections a and c and onezig-zagged seam section b, intermediate sections a and c.

The looped seam sections a and c each have a length of 1.5 cm, and eachconsist of 30 zig-zag stitches.

The zig-zaggcd seam section is 4 crn. along and consists of 20 zig-zagstitches.

The looped seam section a is made so that the stitches are pulledthrough the end of cord 2 and overcast around the cord 1 as shown inmore detail in FIGURE 2, an enlarged View of the cords and seam alongline 2 2 of FIGURE 1.

Similarly, the stitches of the looped seam section c are drawn throughthe end of the cord l and wound around the cord 2, as shown in moredetail in FIGURE 4.

The zig-zagged seam section b is made so that all the stitches are drawnthrough 4the centres of both cord 1 and cord 2 as shown in more detailin FIGURE 3, an enlarged view of the two cords and the seam along theline 3 3.

Joining the cords in the above-described manner may be carried out forexample, on those types of sewing machines which sew various patternsand designs by using exchangeable pattern disks in the sewing machine.

The pattern disks serve to regulate the sewing machine as follows:

l) while the adjacent cord ends are being fed through the machine aconstant stitch interval of 0.5 mm. must be maintained along a distance(section a)=1.5 cm.,

subsequently a cons-tant interval of 2 mm. along a distance of (sectionb)=4 cm., and finally again a constant interval of 0.5 mm. along adistance (section c)=1.5 cm.;

(2) during this transport the stitch width must successively changealong the three aforementioned sections, ie. from about 1.5 rnrn., insection a, to 0.85 mm. in section b and back to 1.5 mm. in section c;

(3) also during this transport along the aforementioned sections a, band c, the path of lthe cords andthe mean position of the stitchingneedle must at the two points of transition be displaced 0.25 mm.relative to each other.

For the-se purposes three pattern disks may be placed in the sewingmachine. For instance use can be made of a sewing machine which isobtainable under the trademark Necchh type Super Nova Julia, automatic534.

it will be understood, of course, that the foregoing disclosure relatesonly to preferred embodiments of the invention and that it is intendedto cover all changes and modifications of the examples of the inventionherein chosen for the purposes of the disclosure, which do notconstitute departures from the spirit and scope of the invention.

W hat is claimed is:

1. A cord fabric comprising a pair of cord ends laid parallel inopposing directions and a stitched seam joining said ends, said seambeing formed of a first section on which the stitches are looped aboutone of said cords and penetrate the body of said other cord, a secondsection of zig-zag stitches penetrating both cords, and a third' sectionin which the stitches are looped about one of said cords and penetratethe body of the other said cord. Y

2. A cord fabric according to claim 1 in which the stitches of the rstand third seam sections are looped `about different cord ends.

3. A cord fabric according to claim 2 in which the length of the rst andthird sections of the seam is at least twelve times the diameter of acord end and the length of the second section of the seam is at leastthirtytive times said diameter.

References Cited in the le of this patent UNITED STATES PATENTS2,126,254

1. A CORD FABRIC COMPRISING A PAIR OF CORD ENDS LAID PARALLEL INOPPOSING DIRECTIONS AND A STITCHED SEAM JOINING SAID ENDS, SAID SEAMBEING FORMED OF A FIRST SECTION ON WHICH THE STITCHES ARE LOOPED ABOUTONE OF SAID CORDS AND PENETRATE THE BODY OF SAID OTHER CORD, A SECONDSECTION OF ZIG-ZAG STITCHES PENETRATING BOTH CORDS, AND A THIRD SECTIONIN WHICH THE STITCHES ARE LOOPED ABOUT ONE OF SAID CORDS AND PENETRATETHE BODY OF THE OTHER SAID CORD.